1. Field of the Invention
The invention relates to a system and method for sealing containment sumps and the like, and is suitable for use with underground storage tanks.
2. Discussion of the Background
Underground storage tanks (“UST”) are used in a wide variety of locations to store materials underground. The stored materials are often harmful to the environment. Examples of such materials include gasoline and other petroleum products, e.g., oil and waste oil, as well as toxic raw materials and waste from manufacturing processes. Because of the harmful nature of these materials, it is especially important to ensure that underground storage tanks containing such materials do not leak or release these materials into the environment.
The use of underground storage tanks for the containment of petroleum fuels and the like is particularly well known. A typical gasoline service station installation comprises one or more underground storage tanks which can be accessed through a removable plate in the apron of the facility, to fill and remove gasoline. Typically, an underground storage tank is also provided with a manway or manhole, if large enough to require access to the interior, through which manway a variety of fixtures, such as a filling device, a submersible pump, and other fixtures as required, are provided. While the fixtures generally penetrate through the manway lid, the manway itself may be provided with a removable lid to access the interior of the tank. While other types of underground storage tanks abound and are within the scope of the present invention, such as cryogenic tanks and the like, the dominant form of underground storage tank is for the storage of petroleum fuels such as gasoline, diesel fuel and the like.
The initial use of underground storage tanks included the preparation of steel tanks, or tanks of various other metal alloys. Steel, being relatively light weight and sufficiently strong to withstand applied pressures, provide sure resistance and the like, provided a building material which could be easily worked with. Examples of such tanks abound in the literature, and steel tanks are made today for such purposes. However, steel and other metal alloys are subject to rust and corrosion. Even in a “dry hole,” that is an installation provided in the ground which does, not fill with water, rain water, ground water and additional sources of moisture such as runoff and the like, will accumulate and the tank is exposed, both from the inside and the outside, to potential corrosion sources. In the worst case, the hole in which the tank is installed may fill, either due to altered surface circumstances like flooding, leading to an accumulation of water in the hole, or commonly, due to a high water table. Under these circumstances, highly corrosive brine may be present also in the hole, as is commonly encountered in coastal sites. Corrosion of the tanks can lead to spot holing, as well as weakened strength, buckling and the like. Whether due to holing or a structural collapse, escape of the contained materials from the confines of the tank due to a failure pose severe environmental hazards. Cleanup of released fuel from a failed tank poses severe time and monetary considerations.
To overcome the tendency of steel to rust and corrode, reinforced plastic tanks have been adopted. Specifically, fiberglass reinforced resin tanks have been used, fiberglass tanks being resistant to corrosion and rusting. The resinous material used as the matrix is selected from a variety of materials, specifically desired to be resistant to penetration by, or adsorption of, the fuels or liquids to be contained, including methanol, ethanol as well as more familiar fuels such as gasoline and the like. A wide variety of resins may be employed in a single tank, including a highly specialized coating (such as a vinyl ester resin) to ensure that the contained material cannot pass into the body of the tank, which may be of a more conventional resin. The fiberglass tanks may be molded off of male forms or female forms.
Persistent concerns over potential environmental hazards have lead to the adoption of “double-walled tanks,” in which the tank containing the fluid material is provided with a surrounding wall, or second wall, such that in the event the interior wall fails, the exterior wall will contain the fluid and avoid release to the environment until repairs can be effected. In the annulus between the inner and outer walls alarm devices of a variety of designs are provided, so as to detect the passage of liquid from the interior tank, or through the exterior tank, into the annulus. In a “dry annulus,” detection of the presence of liquid due to changes in sensed electrical conditions are frequently used. A “filled” annulus tank may use an alarm device which senses a change in the fluid level of the annulus, which will occur upon failure of either the inner or the outer tank. In another alternative, the annulus may be slightly pressurized either positively or negatively, such that a leak causes a drop in pressure which may be detected.
In conjunction with such double-walled tanks, it may be customary to provide double-walled piping from the pump, filling means and the like, or in the case of a single network, piping in and between various tanks. In such a system, the contained liquid is dually contained throughout the system.
In order to access the tank to fill it, to pump fluid out of the tank, to repair the tank and the like, a manway is generally provided into the tank. A releasable cover provided over the manway contains fittings which pass through, and thereby provide a means to pass liquid into and out of the tank. If the tank needs service, and is of a suitable dimension to accommodate a worker, the cover of the manway itself can be removed, to provide access to the interior.
Tanks are generally buried to a standard depth underground. Principal manufacturers of underground storage tanks may provide precise instructions as to the depth, size and character of the hole or opening in which the tank will be set. To access the manway from the surface or apron of the installation, it is necessary to have a clear space or column from the manway to the surface. This is typically provided through a tubular means rising from the surface of the underground storage tank to a point just below the access provided in the ground level of the facility. This device is called a riser.
Frequently, piping accessing the manway will go through the riser to the manway. In order to fill the tank, the manway is accessed by opening the cover in the ground level, accessing the manway through the riser, and providing the necessary liquid material. To ensure dual containment of the fluid wherever it passes, the manway itself may be duly contained by the riser. Where the riser is intended as the secondary containment, or sump, an alarm means is frequently provided in the riser, to detect the accumulation of liquid therein. For the reasons discussed above, such a containment riser (hereafter referred to as a containment sump, or sump) is generally constructed of fiberglass reinforced plastic material, and adhered to the outer wall of the tank, if double walled, by application of resinous material thereto. The sump may be put in place in situ, or provided on the tank.
Recent, repeated severe flooding of many parts of the country has resulted in numerous underground storage tanks where the water level has risen over the top of the sump (indeed, above preexisting ground level) for an extended period of time. Further, the water table in many parts of the country may rise for extended periods to a height exceeding all or part of the riser. Under these circumstances, where there is a sump cover (which must be removable to provide access), the sump cover may be lifted by the water and accumulated liquids pour into the sump, frustrating alarm systems, impeding access to the manway, and providing a potential threat to the integrity of dual containment in a double-walled system.
Also, after a period of time, a build-up of debris/silt may form a dam between the skirt material of the manway and the containment sump allowing water infiltration and build-up of debris/silt surrounding the containment sump. The water/silt build-up may also damage the cover or lid assembly and other components of the sump, making any initial water tight capability obsolete, and thus allowing debris, silt, or water to infiltrate the sump, thus damaging components in the sump and increasing the probability of the water, silt, and debris infiltrating the underground storage tank. Further, when the sump is not water tight it can flood, introducing contaminants to the area outside of the sump, which is often a release point to the environment (soil, groundwater). Spillage of even the smallest amounts build-up over the lifetime of the underground storage tank system and create certain far-reaching environmental problems.
While some attempts have been made to design new systems to prevent water infiltration into UST containment sumps, these systems have various drawbacks, some of which are discussed below, and are not adapted to inexpensively remedy the hundreds of thousands of existing UST's that presently have conventional non-water-tight containment sumps.
For example, U.S. Pat. No. 4,655,361 ('361 patent), which issued to Clover et al., incorporated herein by reference, discloses a Containment Tank. The '361 patent refers to a secondary containment tank and manhole cover assembly. The assembly provides access to a fill pipe for a main underground storage tank and purports to prevent overflow of excess volatile liquid such as gasoline into the ground. The containment tank includes an upper ring or rim secured on an in-ground vertical skirt supported in a concrete base. An inner container is secured to the vertical skirt and has an open end adjacent to the upper ring. The cover fits into and is supported on a horizontal flange or step of the upper ring over the opening of the inner container and includes a vertical ring extending downwardly from the underside of the cover into a space between the inner container and vertical skirt. The vertical ring on the cover extends below the level of the container opening and thus is supposed to bypass surface water leakage through the upper ring around the cover into the space adjacent to the container and into the ground below. The upper containment tank also includes means such as a manually operable sump pump or drain valve to empty excess liquid into the fill pipe of the main storage tank. The system disclosed in the '361 patent would not prevent flooding of the tank in the event of flooding and/or water/silt build-up.
U.S. Pat. No. 4,706,718 ('718 patent), which issued to Milo, incorporated herein by reference, discloses a Containment Manhole having Spillage Sealing Means. The '718 patent refers to a containment manhole comprising a hollow body having a closed bottom and an open top. A concentric opening is provided in the bottom to receive an underground tank fill there through and a circular, resilient seal is provided to seal the junction between the tank fill and the manhole bottom. Optionally, a drain valve may be provided in the manhole bottom to lead any spillage directly back to the tank fill. The manhole terminates upwardly in the machined ring and includes a gasketed junction with the ring. The ring includes an upper shoulder upon which the cover peripheral lip can rest and a lower shoulder of size to enable the cover peripheral edges to rest. An O-ring seal is provided intermediate the cover and the top ring to provide a first sealed junction and a circular gasket is affixed on the lower ring edge to provide a second seal when the cover is in position. In practice this system would be expensive and failure prone. For instance, typically cast iron manhole covers and receptacles would have to be precisely machined to accept a very large and expensive rubber o-ring, which is placed in an orientation and location that would cause it to readily fail in use due to abrasion, wear and tear, and degradation by water/silt sitting right against the sealing surface. Systems utilizing separate manhole covers and sump covers are more practical.
U.S. Pat. No. 4,717,036 ('036 patent), which issued to Dundas et al., incorporated herein by reference, discloses a Liquid Tank Spillage Control System. The '036 patent refers to a spill control device for underground liquid storage tanks having an upwardly extending fill pipe. The control device comprises a steel, epoxy coated, and liquid collecting spill tank having a riser tube that extends upward through the tank bottom. A circular seal ring fits about the upper end of the riser tube and about the outer wall of a fill pipe received through the riser tube. A clamp compresses the seal about both the riser tube and fill pipe. A cover is provided which covers the access opening in the top of the spill tank. A first basin surrounds the cover for channeling precipitation, and other liquids impinging the cover, away from the spill tank. A valve is disposed on the fill pipe for selectively directing liquids discharged into the spill tank into the storage tank. A second basin surrounds the spill tank for recovering liquids discharged from the spill tank during a filling operation. The system disclosed in the '036 patent would not prevent flooding of the tank in the event of flooding and/or water/silt build-up.
U.S. Pat. No. 4,762,440 ('440 patent) and U.S. Pat. No. 4,842,443 ('443 patent), both of which issued to Argandona, both of which are incorporated herein by reference, disclose certain Spill Containment Device(s). The '440 and '443 patents teach spill containment devices for the fill tube of a liquid storage tank, particularly an underground, liquid storage tank. The containment devices each have a spill container with a bottom opening for receiving the tank fill tube in liquid sealing relation to the container wall and a top opening through which the fill tube is accessible for filling the tank, whereby the container is supposed to contain liquid spilled during filling of the tank. The container top openings are closed by removable covers which cooperate with a water drain arrangement to vent liquid vapor from the containers while purportedly preventing rain and other ground surface water from entering the containers. A drain valve operable from a position adjacent each container top opening is provided for draining liquid spill from the respective container to the tank. One embodiment is designed to receive multiple tank fill tubes and has a surrounding casing with a relatively massive top end closure having openings closed by separate relatively small covers which are individually removable to access the different tank fill tubes. The system disclosed in the '440 and '443 patents would not prevent flooding of the tank in the event of flooding and/or water/silt build-up.
U.S. Pat. No. 5,058,633 ('633 patent), which issued to Sharp, incorporated herein by reference, discloses a Containment Assembly for Fill Pipe of Underground Storage Tanks. The '633 patent refers to an assembly intended for use on underground storage tanks. The assembly provides ready access to a fill pipe from ground level. At the same time the assembly serves as a spill containment means for accidental spillage and a secondary containment means for the fill pipe. The assembly of the invention comprises a secondary containment chamber having a sidewall with means for attaching to the storage tank. An anchor ring which is attached to an upper open end of the containment chamber acts as a permanent ground base for the assembly. A bridging surface cover within the anchor ring has a removable lid positioned in its interior portion to gain access to the chamber's interior for a filling operation. The assembly also comprises a fill pipe for delivering liquid to the storage tank. The fill pipe is positioned within the secondary containment chamber with a discharging end extending through the chamber's bottom and a receiving end terminating within the chamber but near the bridging surface cover. An open top spill compartment is positioned within the secondary containment chamber and at the receiving end of the fill pipe so as to encompass the fill pipe's receiving end for the purpose of catching spilled liquid from the filling operation. The spill compartment also is supposed to prevent the spilled liquid and vapors from entering the secondary containment chamber. While sealing the bottom of the secondary chamber is discussed in the '633 patent, the disclosed system would not prevent flooding of either chamber in the event of flooding and/or water/silt build-up.
U.S. Pat. No. 5,222,832 ('832 patent), which issued to Sunderhaus et al., incorporated herein by reference, discloses Spill Containment Devices and Their Installation. The '832 patent refers to a below grade, spill containment device for connection with the riser pipe of an underground fuel storage tank. The containment device is disposed within and isolated from a manhole, which is mounted in a concrete apron. The containment device comprises a compositely formed container, rigidly mounted on the riser pipe. The specially-designed container formed of structural synthetic resin material elements held in assembled relation by snap fitted lugs and notches. A complicated lid assembly, for closing the upper, access opening, includes a pivotable arm. A lever pivoted on the arm selectively engages latch means to lock the lid in a closed position. A projection on the lever prevents the manhole cover from seating if the lever is not in its lock position. A valve for draining fuel from the container to the riser pipe is closed when the lid is open and opened when the lid is closed. The manhole and the containment device are packaged in a shipping carton in spaced relation be corrugated paper sheets. These sheets are employed in obtaining a desired relation between the containment device and manhole in the installation of these components, which involve pouring a concrete apron around the upper end of the manhole. An alternative system employs adjusting nuts to obtain this relationship between the manhole and containment device. This adjusting nut structure pushes down on the lid, but is removed upon installation of the structure. In one embodiment the manhole is compositely formed to permit relative movement between its upper and lower portions, after installation. The '832 patent thus provides one way to attempt to seal a sump lid, but it requires a specially-designed sump container, as well as a very complicated and expensive latching mechanism. The system described in the '832 patent could not readily be used to retrofit existing conventional sumps.
U.S. Pat. No. 7,171,994 ('994 patent), which issued to O'Brien, incorporated herein by reference, discloses a Spillage Containment System and Kit for Underground Storage Tanks. The '994 patent refers to a matter-isolating system for use in combination with an underground storage tank assembly that comprises primary and secondary spillage containment assemblies and a double-walled manhole assembly. The manhole assembly comprises a manhole lid, an outer skirt wall, and an inner skirt wall. The inner skirt wall defines an inner manhole cavity and an outer manhole channel. The outer manhole channel is designed to direct moisture from the lid to certain backfill material in an attempt to isolate the inner manhole cavity from channel-directed moisture. The spillage containment assemblies form concentric primary and secondary spillage-containing chambers in radial adjacency to a tank access conduit of the underground tank assembly. The inner manhole cavity functions to isolate the secondary spillage containment chamber from the outer manhole channel and the primary spillage containment chamber isolates the secondary spillage containment chamber from the tank access conduit. A chamber-monitoring system may be incorporated into the system for monitoring the isolated chambers. The inner manhole cavity, or sump, is provided with a lid having a gasket, but no means is provided to compress the gasket and create a seal, except during temporary pressure testing. The system disclosed in the '994 patent would not prevent flooding of the tank in the event of flooding and/or water/silt build-up.
U.S. Pat. No. 5,595,456 ('456 patent), which issued to Berg, et al., incorporated herein by reference, discloses a Water-Tight Riser For Underground Storage Tank Manway. The '456 patent refers to an underground storage tank provided with a manway equipped with a specially-designed riser or sump extending from the storage tank, about the manway, to a point just below the access way provided in the ground level of the installation. The riser/sump is provided with a “water-tight” domed-shaped cover that is released through operation of a cam mechanism. The riser/sump is intended to exclude water from the interior of the riser/sump and the manway, ensuring access to the manway, operation of the fittings provided in the manway, and an additional containment of fluid passing through the manway and the area of the tank adjacent thereto. An alarm sensitive to liquid may be placed in the interior of the riser to alert the operator to the possible loss of containment, or loss of water-tight sealing between the cover and the riser. Because the '456 patent requires a riser or sump with a horizontal top flange specially configured to mate with a radial clamp, it is not adapted to retrofit the hundreds of thousands of existing UST's that have conventional sumps, which lack this feature. And sump replacement on a buried UST would not normally be feasible, since typical sumps are permanently attached to the UST as originally formed or by application of resinous material.
U.S. Pat. No. 7,043,965 ('965 patent), which issued to Schneider, incorporated herein by reference, discloses a Double-Walled Containment Enclosure. The '965 patent refers to a containment enclosure system at least a portion of which is double-walled. An exemplary system of the invention provides enhanced leak protection by monitoring the space within the double-walled portion of the containment enclosure system. The system is designed to be capable of providing continuous monitoring of the enclosure, collar, penetrations, and/or joints for potential leaks. Several examples are shown of a double-walled containment sump sealed against a double-walled lid such that the spaces within the double-walled portions of the sump and lid are in fluid communication with each other. The examples rely primarily on radial compression of gaskets or O-rings between a vertical lip on the lid and the vertical wall of sump. To effectuate a water-tight seal in such a manner requires significant force. While the '965 patent's thick double-walled components might be able to be designed to withstand such high radial forces, conventional single-walled plastic sumps would simply deflect and deform if attempted to be sealed in this manner, preventing a water-tight seal. For that and other reasons, the '965 patent is not adapted to retrofit existing UST's with conventional single-walled sumps. And sump replacement on a buried UST is not normally feasible as discussed above.
Accordingly, what is needed is a practical system and method for cost-effectively sealing containment risers/sumps, including a system and method for retrofitting existing UST's that have conventional containment risers/sumps, to create a long-lasting, water-tight seal between the riser/sump and its removable lid or cover. Means are also needed to minimize unnecessary instances of lid/cover removal.